﻿EXTERNAL ANATOMY. PERCHING FEET. 131 



in their own tribe, they consequently should possess one 

 structure in common with the crows. Setting these 

 comparatively few exceptions aside, which indicate 

 analogical relations, the equality of the toes in the gene- 

 rality of insessorial birds, when accompanied with 

 slightly curved claws, is a certain indication that such 

 birds live habitually upon the ground, and therefore re- 

 present either the Grallatorial or the Rasorial type ; 

 the birds already mentioned, with hundreds of others, 

 places this position beyond dispute. 



(118.) A perching foot, in the restricted sense in 

 which we now use the term, indicates that those birds 

 which possess it live more among trees than upon 

 the ground. We trace this in the habits of the jays, 

 whose inner toes are more or less shorter than the outer 

 (Jig. 67 .b). The robin, although so frequently seen upon 

 the earth, looking for worms and terrestrial insects, is yet, 

 upon the whole, more arboreal ; and we therefore perceive 

 that its inner toe is very slightly shorter than the ex- 

 ternal one. This disproportion is rather more apparent 

 in the stone-chat (Saxicola rubicola), which, although 

 generally considered a more terrestrial bird than the 

 robin, we should say, from personal observation, was 

 less so ; while in the Motacilla alba, which may be called 

 a truly terrestrial bird, the lateral toes are perfectly 

 equal. The bush shrikes, both of America and Africa 

 (Thamnophilinte), have the lateral toes very unequal, 

 and the claws broad and well curved : this structure is 

 in unison with their manners ; they live only in thickets, 

 the intricacies of which they explore in search of insects 

 and young or sickly birds. We may therefore define a 

 perching foot as of a moderate length, strongly made, 

 with the lateral toes unequal, and the hinder one not 

 lengthened. This latter character, as we shall presently 

 show, being the first indication of a very different type 

 of form. 



(119.) Clinging feet are restricted to the humming 

 birds, whose structure of foot is perfectly unique. 

 From its extreme shortness, on a cursory glance, it 



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